The geographical distribution of endangered species and threatened habitats
should provide useful information for identifying areas in need of special
protection. It is naive, however, to assume that the identification of end
angered species "hot spots" will lead to the development of a system of res
erves that most efficiently protects a maximum amount of biodiversity. To a
chieve this also requires information on the underlying pattern of species
diversity, the distribution of threats to diversity (such as relative rates
of habitat loss), and the value of land in different areas. Here we focus
on information for five U.S. states for which data are available on the und
erlying pattern of overall species diversity in one or more taxa, human pop
ulation density, and land value. We analyze data for plants in California a
nd Texas, birds in Oregon and Iowa, and "herptiles" in Florida. Our analysi
s indicates that the observed distribution of endangered species reflects t
he modification of the underlying pattern of species diversity by anthropog
enic activities. This suggests that a mixture of strategies is required to
protect biodiversity; these should focus on both species and habitats. Our
results indicate that, although protecting wilderness is valuable and relat
ively easy, conserving the most biodiversity will require greater focus on
those areas that are also of highest value to humans.